Adjustable pressure roll for rotary tablet press having self accommodating bridge



June 17, 1958 R. s. FRANK 2,839,015

ADJUSTABLE PRESSURE ROLL FOR ROTARY TABLET PRESS HAVING SELF ACCOMMODATING BRIDGE FiledDec. 12', 1955 INVENTOR. Raymond G. Frank ATTORNEYS 2,839,015 Patented June 17, 1958 ADJUSTABLE PRESSURE ROLL FOR ROTARY TABLET PRES HAVENG SELF ACCOMIVIO- DATING BRIDGE Application December 12, 1955, Serial No. 552,494

6 Claims. (Cl. 107-17) My invention relates to tablet presses, such as rotary tablet presses, which employ a traveling tool assembly including opposing upper and lower punches which cooperate in a die to form tableted products between them as. they are passed between upper and lower pressure rolls. My invention in particular provides a construction for preventing the lower punch from dropping and separating from the tablet as it travels from the lower pressure roll onto an ejection cam.

Tablet presses of the type employing traveling tool assemblies are conventionally arranged to provide for ejection of the tableted product, which can be formed of sugar, phenol formaldehyde resins, ceramics, powdered metals and the like, by passing the lower punch as it leaves the lower pressure roll onto an ejection cam which forces the lower puncli'upwardly in the die to lift the compressed tablet and eject it from the die. Such presses are also conventionally provided with mechanisms for ad justing the relative separation of the upper and lower pressure rolls to permit pressing tablets of different thicknesses. Generally, such adjustment requires that the vertical position of the lower pressure roll vary from one set-up to the next, and hence results in a variation in relative vertical distance from the top edge of the lower pressure roll to the leading edge of the ejection cam. As a consequence the lower punch frequently drops momentarily separating from the tablet as it leaves the lower pressure roll before it is passed onto the ejection cam to force it up in the die and eject the tableted product. Such momentary drop of the lower punch is particularly disadvantageous where the face of the tablet bears characters or the like formed in relief by the end face of the lower punch since it permits a double impression to be made on the face of the tableted product.

It is the primary object of this invention to provide a non-drop arrangement for carrying the lower punch from a pressure roll having adjustable vertical position to the ejection cam which is ordinarily afiixed to the frame of the press.

These and other objects of my invention are essentially obtained by journaling the lower pressure roll on an eccentric horizontal shaft, the angular position of which can be adjusted to set the vertical position of the lower pressure roll and by providing a bridge having a horizontal flat portion enclosing the edge of the lower pressure roll and leading into the ejection cam in a horizontal plane tangent to the upper edge of the pressure roll. Such a bridge is journaled on the eccentric shaft on which the pressure roll is journaled but is provided with a guide which prevents relative rotation of the bridge and yet permits the bridge to move vertically so that as the pressure roll is adjusted in height, the flat surface leading into the ejection cam remains on a horizontal tangent extending from the upper edge of the pressure roll.

For a more complete understanding of my invention reference is made to the appended drawings in which: Fig. 1 is an elevational view, partly in section, of so tates atet @filice 2. much of a rotary tablet machine as is necessary to illustrate my invention;

Fig. 2 is a vertical sectional view through the lower pressure roll and its supporting mechanism taken at line 2-2 in Fig. 1;

Fig. 3 is a horizontal sectional view taken at line 33 in Fig. 2;

Fig. 4 is an exploded isometric view of the lower pressure roll and a portion of its support, including a portion of the bridge and fiat surface;

Fig. 5 is a fragmentary diagrammatic view illustrating lower punch movement across the lower pressure roll onto the ejection cam at one height setting of the lower pressure roll;

Fig. 6 is a view like Fig. 5 illustrating a second height adjustment of the lower pressure roll; and

Fig, 7 is a view similar to Figs. 5 and 6 illustrating a third height adjustment of the lower pressure roll.

In the drawings the reference numeral 10 indicates. a rotary tableting machine of the type generally described in U. S. Patent No. 2,068,169 to Bailey. T ableting machine 10 comprises generally a pedestal mount 11, above which is positioned a rotary tool head 12 which is rotatable about a central vertical spindle (not shown) affixed to pedestal 11. Tool head 12 includes three superposed and spaced tiers which move as a unit. The top tier 13 is a horizontal annular disk provided at arcuate intervals adjacent to its periphery with a series of vertical openings 14 receiving upper punches 15. The middle tier 16 is a horizontal annular disk positioned beneath disk 13 and spaced therefromby neck portion 17. Tier 16 is provided at arcuate intervals with a series of vertical die openings 18 which are vertically aligned with openings 14 in disk 13. The bottom tier 19 is an annular disk which is positioned beneath disk 16 and is spaced therefrom by a neck 20. Tier 19 is provided at arcuate intervals with a series of vertical openings 21 aligned vertically with openings 14 and 15 in disks 13 and 16, respectively, for receiving lower punches 22. The outer edge of disk 19 is provided with gear teeth 23 which cooperate with a worm (not shown) in a conventional arrangement for rotating the entire assembly, including disks 13, 16 and 19, as a unit about their vertical axis above pedestal 11. Head 12 is spaced above pedestal 11 by means of a neck portion 24. Pedestal 11 is provided with a series of cams 26 extending about the periphery of its top surface 25 which cooperate with the heads of lower punches 22 to move lower punches 22 up and down in the conventional manner. These cams include an ejection cam 27. Above head 12 there is mounted, aflixed to pedestal 11, a series of earns 28 which cooperate with the heads of upper punches 15 to move upper punches 15 up and down in the conventional manner.

As is well known in such rotary tablet presses, punches 15 and 22 oppose each other in die cavity 18 to form tableted products between their ends. The general operation commences in a fill position in wihch upper punch 15 is withdrawn from cavity 18 and in which lower punch 22 is depressed slightly in cavity 18. from the'position shown in Figure 1. In the fill position the powdered material which is to be tableted is placed into cavity 18 above punch 22. Thereafter as head 12 rotates from the fill position the operation of cams 28 lowers upper punch 15 into cavity 18 to about the same extent that lower punch 22 extends into" cavity 18. a

The pair of opposing punches are then passed between vertically aligned upper and lower pressure rolls which are mounted on pedestal 11. Upper pressure roll 29 is freely rotatable about a horizontal axis and is positioned such that the lower portion of its edge rides over the head of upper punch 15, forcing punch 15 down in die cavity 18. At the same moment lower roll 30 which is. also mounted about a horizontal, axis, rides under the head of lower punch 22 forcing lower punch 22 up in die cavity 18 opposing the downward movement of punch to compress the powdered material in die cavity 18 between the punches. I

After the compression operation the rotation of head 12 carries upper punch 15 onto a cam which lifts it from die cavity 18. As this action takes place, lower punch 22 rides onto ejection cam 27 which forces the upper end of punch 22 upwardly through die cavity 18 to eject the tableted product. After ejection, cams 26 carry lower punch 22 down to the fill level and the entire cycle is again repeated. In actual practice, of course, head 12 will carry a number of such opposing punches to which I shall hereinafter refer, together with their associated die cavities 18, as tool assemblies. The press, moreover, can be constructed to provide more than one cycle of operation in a single rotation of the tool head.

Insofar as tablet press 10 has been described above, its construction is entirely conventional. My invention is particularly concerned with the manner in which lower punch 22 is carried from pressure roll 30 to ejection cam 27. Referring more particularly to Figs. 2, 3 and 4, it will be noted that pressure roll 30 is journaled on the eccentric central portion 31 of a horizontal shaft 32, the inner end of which is journaled in the shell of pedestal 11. The outer end of shaft 32 is journaled in an adapter 33 which is affixed in another portion of the shell of pedestal 11. The outer end of shaft 32 projects outwardly from adapter 33 and carries segmental worm gear 34 which is operated by a worm 35 mounted on pedestal 11 and in turn is operated through a right-angle take-off by a hand wheel 36. It is thus apparent that rotation of hand wheel 36 rotates worm 35 and in turn segmental gear 34 to rotate shaft 32 and thus raise or lower the axis of eccentric portion 31 and hence raise or-lower pressure roll 30.

A roll bridge 43 extends about both sides of pressure roll 30 and is provided with a portion 37 extending from the edge of pressure roll 30. On portion 37 there is mounted a flat curved cam 38, the upper surface of which lies in a horizontal plane tangent to the upper edge of pressure roll 30. Cam 38 curves slightly, in conformity with the circle of rotation of the heads of lower punches 22, and fits into a recessed portion 27a of ejection cam 27. The width of cam 38 where it enters recessed portion 27a is extremely narrow and just sutficient to support the weight of punches 22, such that the heads of punches 22 will ride onto the surfaces of earn 27 which extend to both sides of cam 28 where it enters recess 2711.

Roll bridge 43 is journaled on eccentric portion 31 of shaft 32 by a pair of rectangular blocks 39, one disposed on each side of pressure roll 30, which are provided with central bores for rotatably receiving eccentric portion 31 and which slide horizontally in horizontally elongated rectangular slots 40 in each side of roll bridge 43. One side of roll bridge 43 is provided with a pair of vertical bosses 41 extending above and below slot 40 which define between them a vertical channel in theside of roll bridge 43 which slidingly receives a vertical tongue 42 on the inner face of adapter 33.

It will be apparent, therefore, that as pressure roll 30 is raised and lowered by rotating shaft 32, roll bridge 43 is similarly raised ,and lowered. The horizontal sliding movement of slide blocks 39 permitted by theelongated shape of slot 40 causes roll bridge 43 to rise. and fall vertically only with sliding cooperation between tongue 42 and bosses 41. Since roll 30 moves vertically with a circular movement the separation between ,tangential cam 38 and the upper edge of roll 30 varies during the height adjustment. The maximum clearance (see Figs. 5 and 7), however, is always less than the width of the flat bottom surface of the head of lower punch 22.

Referringto Fig. 5, it will be observed that as the head of lower punch 22 rides from cam 26 onto roll 30 (adjusted to its maximum down position) punch .22 is forced slightly upward to compress the powdered material in die 18. As punch 22 continues to move it passes onto the horizontal and tangential surface of cam 38 without any drop and then is carried into ejection cam 27 which thereupon raises the punch. Precisely the same operation occurs when the roll bridge 43 and pressure roll 30 are, adjusted to an intermediate height as illustrated in Fig. 6 and when they are adjusted to maximum height as illustrated in Fig. 7.

I claim:

1. In a tablet press including a frame, a die head moveably supported on said frame, a vertical die opening in said head, a punch positioned beneath said head having its upper end extending into said die opening, a pressure roll positioned beneath said die head, an ejection cam positioned on said frame beneath said die head adjacent to said roll, and means for moving said die head horizontally relative to said roll and ejection cam to carry the lower end of said punch over the upper edge of said roll and onto said ejection cam, the improvement which comprises an eccentric shaft supported horizontally at its ends on said frame for eccentric rotational movement,.said pressure roll being journaled on said eccentric shaft for free rotational movement, a bridge having a portion defining a fiat surface extending from the edge of said pressure roll in a horizontal plane tangent to the upper edge of said pressure roll, the outer end of said flat surface leading into said ejection cam, journal means supporting said bridge on said eccentric shaft to permit said bridge to move horizontally with respect to said shaft and to prevent said. bridge moving vertically with respect to said shaft,,and guide means to permit said bridge to move vertically with respect to said frame and to prevent said bridge from moving horizontally with respect to said frame.

2. In a tablet press, the improvement according to claim 1 in which said journal means comprises means receiving said shaft in sliding rotational contact therewith, and received by said bridge in horizontal sliding contact therewith.

3. In a tablet press, the improvement according to claim 1 in which said journal means comprises a rectangular block having a transverse bore receiving said eccentric shaft and received in horizontal sliding contact in a horizontally elongated slot in said roll bridge.

4. In a tablet press, the improvement according to claim 1 in which said guide means comprises means mounted on said frame slidably engaging said bridge in a vertical direction.

5. In a tablet press, the improvement according to claim 1 in which said guide means comprises a vertical tongue mounted on said frame slidingly received in a vertical slot in said roll bridge.

6. In a tablet press, an eccentric shaft, a roll journaled on said shaft, a bridge having a portion defining a flat surface extending from the edge of said roll in a plane tangent to the edge of said roll, journal means supporting said bridge on said eccentric shaft for confining movement of said bridge relative to said shaft in a direction at right angles to the eccentric axis of said shaft and parallel to said tangent plane, and guide means for confining relative movement of said bridge with respect to said press in a direction at right angles to said tangent plane.

References Cited in the file of this patent UNITED STATES PATENTS 1,698,852 Miller et al Jan. 15, 1929 2,043,085 Westin et a1. June 2, 1936 FOREIGN PATENTS 25,298 Great Britain Nov. 9, 1906 321,748 Great Britain Nov. 21, 1929 

